1. Field
The presently disclosed subject matter relates to a liquid crystal display (LCD) apparatus, and more particularly to an LCD apparatus having a high visual quality, which allows wiring lines to have reduced impedance variations among electrodes connecting to the wiring lines for driving a liquid crystal layer disposed between respective electrodes, and thereby reducing display variations among display patterns (pixels in a matrix type LCD) in a segment type LCD.
2. Description of the Related Art
Segment type LCD apparatuses have been used as a display apparatus for various equipment such as home electric appliances, office automation equipment, automobile parts, etc. One of the reasons is that the segment type LCD apparatuses enable a single segment to form a display pattern in various shapes at low cost as compared to a matrix type LCD apparatus.
In the segment type LCD apparatuses, the display pattern can be formed between transparent electrodes (a common electrode and a segment electrode), which are respectively provided on two transparent substrates (e.g. glass substrates). Specifically, a desired display pattern can be formed by patterning a segment electrode in the desired shape on a transparent substrate and by patterning a common electrode corresponding to the segment electrode on another transparent substrate.
In this case, the segment electrode and the common electrode are connected to wiring lines, which receive a power supply therebetween. Each of the wiring lines can be formed by patterning the respective wiring lines along with the segment electrode and the common electrode on their transparent substrates, respectively. In general, each of the wiring lines for the segment electrode and the common electrode is located so as not to overlap with respect to each other. That is typically done to prevent an undesired display (lighting) in a region where the wiring line for the segment electrode intersects with the wiring line for the common electrode.
When a display density of the display patterns and the like is high due to many segments in LCD apparatuses such as the segment type LCD apparatus, a character type LCD apparatus, a graphic type LCD apparatus and so on, an available area for each of the wiring lines connecting to the segment electrodes and the common electrodes becomes very small. Thus, each of the widths of the wiring lines is typically reduced. The wiring lines are generally formed of transparent oxide semiconductors such as ITO, for which resistivity is approximately 10−4 ohm cm and therefore is high as compared to a wiring line that is made of a metal.
Consequently, the narrower each width of the wiring lines is, the higher that each of the resistance values of the wiring lines is. As a result, a voltage applied between the segment electrode and the common electrode may be reduced, because not only are there voltage drops between both ends of the wiring lines connecting to the segment electrodes (which voltage drops can be high) but there are also voltage drops between both ends of the wiring lines connecting to the common electrodes (which also can be high).
In the segment type LCD apparatuses, because each shape of the wiring lines (for example, the lengths and widths of the wiring lines) connecting to the common electrodes may be different, each of the resistance values between both ends of the wiring lines can be different. The resistance differential of the wiring lines may cause differing variations among voltages applied to the common electrodes. Each of the shapes of the wiring lines connecting to the segment electrodes may also cause variations among voltages applied to the segment electrodes due to the same above-described reason.
The variations among the applied voltages may cause differing variability of optical transmittance among display patterns of a liquid crystal layer, which is disposed between the segment electrodes and the common electrodes. The transmittance differential may cause differing display variations such as in brightness, color tone and the like among the display patterns. The variations among the display patterns may also result in degradation of the visual quality of the display as a whole.
In order to prevent this variation between the pixels (the display patterns in the segment type LCD), a conventional LCD apparatus shown in FIG. 13 is disclosed in patent document No. 1 (Japanese Patent Application Laid Open H05-203997). The conventional LCD apparatus includes pixel electrodes 56a and 56b, and wiring lines 52a and 52b that extend from the pixel electrodes 56a and 56b toward a peripheral region thereof, respectively. In addition, compensating electrodes 50a and 50b are located between the peripheral region and the pixel electrodes 56a-56b and are located on the opposite side of the wiring lines 52a and 52b via a liquid crystal.
In this case, the large compensating electrode 50a is located on the opposite side of the short wiring line 52a, and the small compensating electrode 50b is located on the opposite side of the long wiring line 52b. That is, a large capacitance of the liquid crystal is formed on the short wiring line 52a of which resistance value is small, and a small capacitance of the liquid crystal is formed on the long wiring line 52b of which resistance value is large.
Therefore, even when the respective resistance values of the wiring lines 52a and 52b are different due to their lengths, their resistance values may substantially become equal to each other because the compensating capacitances of the liquid crystal on the short wiring line 52a and the long wiring line 52b may compensate for their resistance differential.
The above-referenced Patent Document is listed below and is hereby incorporated with its English abstract in its entirety.
1. Patent document No. 1: Japanese Patent Application Laid Open H05-203997
However, the conventional LCD apparatus does not only need the regions for the pixel electrodes to control the LCD display but also needs new regions for the compensating electrodes. In addition, shapes of the compensating electrodes respectively are typically adjusted in accordance with the respective shapes of the wiring lines, because overlapping areas between the compensating electrodes and the wiring lines are individually adjusted. Thus, in the conventional LCD apparatus, there are problems in that, for example, the structure may become complex and large.
The disclosed subject matter has been devised to consider the above and other problems, characteristics and features. Thus, an embodiment of the disclosed subject matter can include an LCD apparatus having a high visual quality and a simple structure. In this case, each of the effective voltages applied to display patterns (pixels) of the LCD apparatus can be adjusted without additional compensating electrodes by adjusting impedances among the display patterns (the pixels) with wiring lines. Thus, the LCD apparatus can result in a high visual quality with a simple structure. In addition, the LCD apparatus can be driven by a simple driving circuit as usual.